Vapor-electric device



July 29, 1952 J. BOYER ET AL VAPOR-ELECTRIC DEVICE A Filed Jan. 15,19.51

lNVE L.Boy ert J Boll NTORS John er and Rob 0rd. BY

ATTORNEY Fig.l.

WITNESSES: 4W

i atented July 29,

2,605,439 'VABOHsELECTRI-C. DEVICE- John L.'B'oyer, Pittsburgh, andRobert .LBaIIai d; West Newton, Pa.', assignors t'o WestinghouseElectric Corporation, East Pittsburth, raga corporation of Pennsylvania,

Application 'Ja s, 1951, Serial.No .-205,8 99.

Our invention relates to vapor-electric 'de- .vices or. tubes, andparticularly to low-arcj-drop h otscathode arc-discharge devices'usingavap'o'ri zable discharge-metal selected from the group consisting ofpotassium, rubidium and. cesium. Our present invention is animprovementover .the vapor-electric devices; which are described andclaimed in anapplicationof John L. Boyer densed on the; anode, asin previousdesigns.

This condensation-place of the discharge,- metal; is. determined bymaking; the; cold; end; of thecathode the, coolest. part of the tube.This has; the. double advantage, of. getting the. discharge-metalpool atthe cathode-potential, in a place where. it. is protected. againstpositive-ion bombardment under all conditionsof operation.Thedi'scha'rge-metal pool, at the cold end; ofithe cathode; is also. at.a. spot. at which the 3 temperature is not materially afiected by theintensity of the; arc, andhence not. materially; afiected by: the.load-current, as in; previous tube-designs in; whichthe dischargermetalpool was: at or near apart. of the anode.

Ourflmounting of. the grid. on. an externally cooled metalenclosure-portionof, the tube enables: us. to" maintain the grid. at: a.much cooler temperature than has been heretoforepossible with-any othergrid-mounting, with the result thatwe areinow freedofthe necessityforchoosing,. for the grid-surface 'materiaL. a. metal having. a lowwork-function, such as was reduired in: the tube-construction shown inthe Boyer- Colaiaco' application.

As explained in the Boyer-Colaiaco. application, the three preferreddischargeemetals,

potassium, rubidium'a'n'd cesium, form a; more or: less" distinctiveclass by themselves, iwhich may be: described. as the: alkali: metalshaving four, five. and sixr'shells'in theiratomic: structure, orfathetstable alkali metals having. more .than three shells; The entire groupoti'alkali iiietalsl consists. of. six' elements, 'of which J the..firstj two: and the last are readily clistin'guish-- alkali-metalgroup (-IA); as being distinctiv'e beis called. franciiim (Emma ofdesign and opera 1 011,} hereinafte invention,

.d a 'e'd by the: Me i 1 c o truc i n:- Q he id-H in ud ng; t n-an bpt emi c flk lt-1 9st eenhe-" ot om; t t a -.mt.& n 6 and the: top of thecenter. metal portio 2 able from the othe three, with which o ii''iirventi'onis: ticularlyjc n e ied 'Thejtwo lightest; alka lfmetals;lithium KL-ii) and sodium (Nalare separated, some peri odib names; fromthe heavier; light assive-urge cause of their;'electron-grquping. Theand chemical characteristics.of.-thes two 11 alkalie-metals'are alsod'istinetivelyfdi-fierent from the ou "s nri's i lidta si im. d ce iu'sodi'umh s ir-m nimum. voltage. which. comes'attoo low a; pr sstancegproduct' palTfbr "ourg'purp s; a w understood. from"explanation'and it," is a1'S0.-t.OD altitivje, N a. an rnre flr which 8 much. to 10our .purpo s,', a'sfthisf'lowvapoFpressiir quires too] ghaitempera'turetq obtain 1 tically usable. vapoiipressiir'ejwhich"Bisenough o give l i n ylhishmirmntrdemi to be practical romur 'purbbses. j

The sixth or, heaviest, alkali. metal; .No, 8!; in the periodic tablevv'as.f'ci' ri'nerly''calledvir but has n w beenprmiedrc'b product whichvery radiolactive a has an. extremely sricrt. half -lifef. Iminutes,'-so that itjis' unsuit le {or 0 9 0 r :2 tures,. combinatiqnsgsyst in drawing; wherein Figure 1 is. a, vertical,sectional, view of. aggreferred illustrated form of. embodiment. of;'ciiir and claimed}. and illustrated. in. aqcomp 5g- Fig. 2 is ahorizontal sectionah v w, om h t: larger ale .1 h 1 broken away,

F g, 3 isa plan vi i. an; s eam illar a w mrarts r k l Fig. 4 is avertical sectional vie shown Fig. 3.,

In. the exemplary form ofi. embodi' inv n i n ts-show device. comprisesa vertic l and a -Qen al metal po tion 8 a l f: w ich: e i ustra ed: as;he ss bi la there is disposed a tubular insulator-portionfidl ,rentrantcathode-tube 28.

which may be glass, and which is connected to the metal portions bysuitable glass-to-metal seals. Between the bottom of the central metalportion 8 and the top of the bottom metal endportion 7, there is anothertubular insulatorportion. l3, which may also be of glass, and which isprovided with suitable glass-to-metal seals to the respective metalportions.

The top metal end-portion 6 is closed at its upper end, either by anintegral end-part, or a I brazed or welded connection to a separatemetal piece I6, which is preferably a. reentrant portion which extendsdown below the top tubular insulator-portion 9, and which terminates,atits lower end, in an arc-terminating metal anodeportion [1.

The three metal enclosure-portions 6, 7 and 8, and the metalanode-portions I6 and I! are all preferably made, either altogether of ametal chosen from thegroup consisting of iron and between the coppercore 20 and the iron anode surface-parts l6 and IT. The coppercore-parts and the copper fins serve as excellent heat withdrawingmaterials, of good heat-conductivity, for

withdrawing heat from the arc-terminal anodeportion H, which gets quitehot by reason of the playing of the arc thereon, during the operation ofthe tube. Frequently, it is desirable to provide the copper anode-core20 with a central hole 24 in which an anode-heater25 may be placed foroccasional use in controlling the anodetemperature, as may be required.

The lower metal end-portion '7 of the enclosure is provided with abottom closure-means 21, which is perforated to receive an upstandingThe cathode-tube 28 is preferably made of nickel, or at least itssurfaces which ar exposed to the vapors within the device are preferablymade of nickel, as explained, in the Boyer-Colaiaco application, and asis known inthe art of alkali-metal-tube-design. It will be understood,of course, that the 'bottom-member2'l is either integral with, or

tightly welded or brazed to, the bottom metal endportion 1 of theenclosure, and that the cathodetube 28 is either integral with, ortightly welded or brazed to, the bottom end-closure 21. This bottomend-closure 21 may be either iron (including steel) or nickel. V

The top end of the rentrant cathode-tube 28 is closed, as indicated at32. About half of the total length of the cathode-tube 28, at the topend thereof, is provided with radial fins 33, of the same material(nickel) as the cathode-tube 28, as explained in the Boyer-Colaiacoapplication.

In common with other known types of hotcathode alkali-metaldischarge-devices or valves,

the active cathode-portion, which is the finned The bottom metalenclosure-part I, which carries the cathode, is exposed to the ambientatmosphere, which usually provides sufiicient cooling to make the lowerend of the cathode-tube 28 the coolest part of the tube. The portion ofthe cathode-tube 28, below the finned upper end thereof, is madesufficiently long, and, if necessary, sufficiently thin incross-section, so as to reduce the rate of heat-conduction from the hotupper end of the cathode-tube 28 to the cool lower end thereof, thusassisting in maintaining the cool temperature-conditions at said lowerend.

The open lower end of the rentrant cathodetube 28, which extends downbelow the base-portion 21 of the enclosure-means of our tube, isprovided with any suitable closure-member 40, which includes a suitableinsulating-seal M for introducing the heater-terminal 42 for thecathode-heater 31.

It is usually desirable to protect the lower tubular insulator-portionI3 of the enclosure-means from the temperature of the cathode-tube 28,which is done, in the illustrated embodiment of our invention, by meansof a plurality of concentric metal baffles 33, which are carried by aninverted cup-shaped metal member M which encircles the cool lower end ofthe cathode-tube 28, so as to be supported thereby. The open end of thiscup-shaped member 44 faces downwardly toward the cathode-end of ourtube, that is, toward the bottom end-closure member 21.

It is a feature of our invention that we use this inverted cup-shapedmember 44, and the space between it and the bottom end 2'! of the tube,as a place for locating our evacuating-tube 67, the inner end of whichwe extend into the tube to a point between said lower end 21 of thedevice and the open bottom end of said cupshaped member 24. Thisevacuating-tube 41 is used for evacuating the internal space within ourtube, and when this evacuation-process is completed, the outer end ofthe evacuating-tube A! is commonly sealed off, as indicated at 68.

However, before sealing off the evacuatingtube 61, it is customary touse this tube for introducing the small amount of alkali metal which isneeded for the operation of the tube, this alkali metal being commonlyintroduced by in some way breaking an ampule containing it, in theevacuating system, usually in such a way that the wreakage of the ampuleitself will be maintained in the evacuating system and will not beintroduced into the container of the dischargetube. For this purpose, itis convenient to turn the tube temporarily upside down, while the alkalimetal is being introduced, so that the introduced material will becaught within the cupshaped member 44. In this way, the initial chargeof the alkali metal will be entrapped in the space defined between theinverted cup 44 and the bottom end-closure 2! of the tube, and sincethis is the coolest part of the tube, in operation, the condensed alkalimetal will always be collected in this portion of the discharge-deviceor tube.

Since this cooling or condensing-place for the alkali-metal pool (whichmay be only a few drops) is at the/cold end of the cathode, thisalkali-metal pool is at the cathode-potential, and it is also fairlywell shielded (by the inverted cup-member 44) from the are which playsfrom the finned cathode-portion upwardly onto the lower end of the anodel7. Since the alkalimetal pool is thus at the cathode-potential, it

grid, soas to improve:theheat-radiation from p the grid.

In a grid-controlled vapor-electric. dischargetube, the grid issubjecttothe greatest heating, of all the parts of the tube; because itis necessarily enveloped inzthe hot arc. In previous tube-de- I signs,the grid has been thermally isolated from of the anode of thedevice,because. the lower end of the cathode is inherently much thebetterplace, since. its temperature is notaffected by thezintensity of thearc, and hence it is :not affected .by the load-current of the device.

As/explained at the outset :of our description,

- theialkali-metal which .we useifor our discharge- :metal is selectedfrom the'groupv consisting of .potassium,.rubidium andv cesium. Atpresent we prefer cesium, for most types of tubes with which our.experience has been mainly directed, 'although potassium and rubidium.are both-possible .ialternatives, particularly for icertaintube-characteristics. Whencesium is the discharge-metal,

- theacold lower end of the cathode-tube 28. iskept between thetemperatures of 130? and 180- C. .during the operation of the tube,while the upper hot end is kept betwen 650 and 850C. When rubidium isthe discharge-metal, thecoldend of the cathode-tube28 is kept between.180 and 2259 C., and thehotendbetween 700and 900 C. When potassium isthe discharge-metal, the cold end of the cathode-tube 28 is kept between260 .andBlO" C., and the hot end between .800" and 900 C. These are thetemperature ranges which at present seem preferable, in the operation of1 our device. v

. In .common with other finned-cathode. alkali- .metal tubes, it isdesirable to place a suitable thermal guard around the finned portion 33of thencathode. In our illustrated construction, the lower end of our.finned cathodeeportion 33 is thermally guardedyor heat-insulated fromthe :bottom end ZLof the enclosure, by. means ofthe invertedcup-memberAmand the concentric cylindrical meal heat-shields 43.

It is necessary, also, to thermally guard the lateral sides orperipheries of the fins 33, which we have done by theprovision oftwoclosely-ispaced, but separated, concentric metal tubesor cylinders53, which are disposed between the fins33 and thetadjacent side-walls ofthe enclosure-meansfor the tube,

being spaced from both, and being-supported by a plurality of stiffvwires 54 from one of the cylindrical guards-43. In our device, the arcplays upwardly from the finned portion 33, so that it is possible forthe laterally disposed thermal guards or heat-shielding means 53 to beimperforate'cylindrical or tubular members.

. .iMost'tubes of the type to which-our invention relatesaregrid-controlled tubes, andour present invention is primarily adapted forsuch tubes.

:O'ur new tubeconstruction and arrangement en- -.enclosure-portion 8,thus giving'our grid a heat- :conducting or radiating means'which isdirectly cooled by the ambient atmosphere, (or by other externallyappliedcooling-means). *Usually, if

atmospheric cooling is relied upon, itwill be desirable .to. usecooling-fins B2,. whichj-are carried by the casing portion: 8 at the."position I of the than has heretofore ever been possible.

all external connections, and it has run at very high temperatures,notwithstanding all that could be done in the way of shielding itfromthe necesarily high temperature of the cathode, and increasing theheat-radiation from the grid to theanode, which has always beenexternally cooled. This high operating-temperature of previous grids hasnecessitated a resort to lowwork-function metals, for the grid-material,as explained in the Boyer-Colaiaco application.

In our present invention, we, are :able to operate the grid 60 at a muchcooler temperature In 'a cesium tube, it is necessary to operate thegridcooling envelope-portion 8 at a temperature which is at least ashigh as about 200 C., in order to prevent condensation of cesiumthereon, and in our invention We make our design so that thisenvelope-part 8 will run at somewhere around that temperature. Therewillnecessarily be some temperature-drop between the hottest point ofthe grid 60 and the envelope-portion 8, and the rating of the tubedepends in large measure upon the temperature to which the grid can beheld. In a cesium tube, 315 C. is about the temperature at whichemission starts to be heavy enough to hurt, on the grid 60. It is to beunderstood, of course, that these temperature-figures are illustrativeonly, and that slightly different temperature-limits will beencounteredwhen the discharge-metal is either potassium or rubidium.

As'to the gridematerial, we are no longer limited tolow-.work-functionmetals, and We may prefer not to use such metals.Copper wouldbe an ideal material for the grid 60, except for thenecessity for degassing the tube, 'duringthe process of evacuating it,at which time temperatures of the order of 900 C.,.or more, are used fora brief time, but this will evaporate Jenough copper, from any exposedcopper surface, to cause a very damaging copper-condensation or depositon the other internal parts of the tube. At least the surface-portionsof the grid 60,'whicn are exposed to the vapors of the tube, that is,

which are exposed to the interior of the tube,

should be made, therefore, of a material which is able to resistvaporization at the degassing ternperature, even though this material isnot as good a heat-conductor as copper, as in geenral it will not be. Asuitable material for the grid,

'or for the grid-surface, is a low-carbon steel,

its periphery is thickened so as to present a broad contact-surface,which is brazed to the enclosure-portion 8, preferably by using a smallamount of copper. It is possible, however, to make the grid of copper,with a protective plating, coating or surface-covering of iron, asindicated at 64 in the broken-away portion of the grid 60 in Fig. 1.

Alternatively, as shown in Figs. 3 and 4, the

grid 60 might be made of iron or steel, with a number of copper inserts66, which enter into radial holes in the iron material of the grid, fromthe periphervofthe grid, and thus aid in carrying heat radiallyoutwardly from the center of the grid to the casing-wall 8.

1 In our improved tube-design, it will be noted that the axial arc gapseparation or spacing is extremely small, thus contributing to a lowarc-drop. This arc-gap spacing is only enough to provide for thethickness of the grid, and a suitable spacing between the top and bottomgridsurfaces and the anode and cathode, respectively.

It will be noted that, (in our preferred design at least), no shieldingof any kind is needed, between the grid, on the one hand, and the anodeor the cathode, respectively, on the other hand.

Our direct cooling of the grid 60, by reason of its thermal connectionto an external wall of the tube, makes it possible for us to maintainour grid 60 at the extremely low operating-ten'iperatures which havebeen above described.

While we have illustrated our invention in a single illustrative form ofembodiment, with some suggestions regarding alternative forms of thegrid, we wish it to be understood that the forms shown are merelyintended to be illustrative, and we desire that our appended claimsshall be accorded the broadest construction consistent with theirlanguage.

We claim as our invention:

1. A vapor-electric device comprising an enclosure-means including twometal end-portions, a tubular central metal portion, a tubularinsulator-portion between each end of the central metal portion and theend of the corresponding end-portion, and insulator-to-metal sealsbetween each end of each tubular insulator-portion and the end of theadjacent metal portion; an arcterminating metal anode-portion carried byone of said metal end-portions of the enclosure; an arc-terminatingfinned metal cathode-portion carried by the other metal end-portion,said oathode-portion including a reentrant metal tubeportion having aclosed inner end carrying the cathode-fins; a quantity of adischarge-metal within said device, said discharge-metal being selectedfrom the group consisting of potassium, rubidium and cesium; acathode-heater within said reentrant metal tube-portion; means forexternally cooling a substantial part of the external portions of saidenclosure-means, including said tubular central metal portion; and ametal gridmember carried by said tubular central metal portion in goodthermal contact therewith, said grid-member being disposed transverselyacross the vapor-electric device, between the arc-terminatinganode-portion and the arc-terminating finned cathode-portion.

2. The invention as defined in claim 1, characterized by the surfaces ofthe metal enclosureportions which are exposed to the vapors within thedevice being of a material chosen from the group consisting of iron andnickel.

3. The invention as defined in claim 1, characterized by the surfaces ofthe grid which are exposed to the vapors within the device being of amaterial chosen from the group consisting of iron and nickel.

4. The invention as defined in claim 1, characterized by the surfaces ofthe grid and the metal enclosure-portions which are exposed to thevapors within the device being of a material chosen from the groupconsisting of iron and nickel. V

5. The invention as defined in claim 1, characterized by the surfaces ofthe grid and'the metal enclosure-portions which are exposed to thevapors within the device being of a material chosen from the groupconsisting of iron and nickel, and further characterized by the surfacesof the cathode-tube and cathode-fins which are exposed to the vaporswithin the device being or nickel.

6.'The invention as defined in claim 1, characterized by thecathode-heater being concentrated at the finned end of the cathode-tube,

.and said cathode-tube being long enough so that its otherend, which isadjacent to the cathodeend of the vapor-electric device, is the coolestpart of the device, whereby the discharge-metal condenses thereon.

'7. The invention as defined in claim .1, characterized by thecathode-heater being concentrated at the finned end of the cathode-tube,and said cathode-tube being long enough so that its other end, which isadjacent to the cathodeend of the vapor-electric device, is the coolestpart of the device, whereby the discharge-metal condenses thereon, andfurther characterized by said device having a plurality of spacedconcentric tubular metal heat-shields supported between the cathode-finsand the surrounding wallportions of the enclosure-means.

8. The invention as defined in claim 1, characterized by thecathode-heater being concentrated at the finned end of the cathode-tube,and said cathode-tube being long enough so that its other end, which isadjacent to the cathodeend of the Vapor-electric device, is the coolestpart of the device, whereby the discharge-metal condenses thereon, andfurther characterized by said device having means providing a cup-shapedmember surrounding the cold end of the cathodetube within the device,the open end of said cupshaped member facing that end of the device,

- and an evacuating tube extending into the device to a point betweenthat-end of the device and the open end of said cup-shaped member.

9. A vapor-electric device comprising'an enclosure-means, an anode, acathode, and a quantity of a discharge-metal within said device, saiddischarge-metal being selected from the group consisting of potassium,rubidium and cesium; said cathode including a rentrant metal tubeportionextending into said enclosure-means, said cathode-tube having a closedinner. end, metal fins carried by said cathode-tube near said closedinner end, a cathode-heater disposed within said cathode tube, saidcathode-heater being concentrated at the finned end of the cathodetube,means for externally cooling the enclosureentering end of thecathode-tube, said cathodetube being long enough so that itsenclosureentering end is the coolest part of the device, whereby thedischarge-metal condenses thereon, and means providing a cup-shapedmember surrounding the cold end of the cathode-tube within the device,the open end of said cup-shaped memconsisting of potassium, rubidium andcesium;

said device having means providing a cup-shaped member, the open endofrsaid cup-shaped memher facing an enclosure-wall so as to provide apartially enclosed pocket within said device, and an evacuating tubeextending into said pocket.

11. A vapor-electric valve comprising a substantially tubular envelope,a cathode at one end of said envelope, an anode at the opposite end ofsaid envelope, said envelope having an intermediate metal sectioninsulated from said anode andsaid cathode, a metal grid disposedtransversely across the valve, between said anode and said cathode, ingood thermal contact with said intermediate metal section, and externalcoolingmeans for said intermediate metal section.

12. A vapor-electric valve comprising a substantially tubular envelope,a cathode at one end of said envelope, an anode at the opposite end ofsaid envelope, said envelope having an intermediate metal sectioninsulated from said anode and said cathode, a metal grid disposedtransversely across the valve, between said anode and said cathode, ingood thermal contact with said intermediate section, and an externallyprojecting radiator disposed in good thermal contact with saidintermediate metal section in opposed relation to said grid.

13. An electric valve comprising a container having a substantiallytubular wall-portion, a cathode extending axially into said container, aheater disposed within the extreme inner end of said cathode, a thermalshield interposed between said inner end of said cathode and the sidesof said cointainer, means disposed behind said inner end of said cathodefor providing a cup-shaped member, the open end of said cup-shapedmember facing that end of the container, an evacuating tube extendingthrough a portion of said container at cathode-potential and extendinginto proximity to the open end of said cup-shaped member, an anodedisposed at the opposite end of said container in opposed relation tosaid cathode, and a quantity of a discharge-metal within said container,said discharge-metal being selected from the group consisting ofpotassium, rubidium and cesium.

14. An electric valve comprising a container having a substantiallytubular metal wall-portion, a cathode extending axially into saidcontainer, an insulating seal between said cathode and said tubularmetal wall-portion, a heater disposed within the extreme inner end ofsaid cathode, a thermal shield interposed between said inner end of saidcathode and the sides of said container, means disposed behin said innerend of said cathode for providing a cup-shaped member, the open end ofsaid cup-shaped member facing that end of the container, an evacuatingtube extending through a portion of said container at cathode-potentialand extending into proximity to the open end of said cup-shaped member,an anode disposed at the opposite end of said container in opposedrelation to said cathode, an

insulating seal between said anode and said tubuductivity, andsurface-portions composed of a metal having less thermal conductivitybut having a lower vapor-pressure at a temperature of the order of 1000C.

16. A metal-vapor electric discharge-device comprising a closedenvelope, a heated cathode extending into one end of said envelope, ananode at the opposite end of said envelope, said envelope having anintermediate metal section insulated from said anode and said cathode,and a metal grid disposed transversely across the device, between saidanode and said cathode, in good thermal conducting relation to saidintermediate metal section of the envelope, the discharge-metal of saiddevice being selected from the group consisting of potassium, rubidiumand cesium.

17. A metal-vapor electric discharge-valve-comprising a cathodestructure, means for heating said cathode, a heat-shield substantiallyenclosing the sides and back of said cathode, the back portion of saidshield constituting a rearwardly extending cup-shaped portion, a tubularmember extending through a portion of the device at cathode potential,said tubular portion member extending into the area defined by saidcup-shaped portion, an anode spaced from the exposed front portion ofthe cathode, an intermediate metal enclosure-portion extending betweensaid anode and cathode, said intermediate metal enclosureportion beingsealed in insulating relation to said anode and said cathode to providea closed container, and a grid interposed between said anode andcathode, said grid being in good thermal contact with said intermediatemetal enclosure-portion, the discharge-metal of said valve beingselected from the group consisting of potassium, rubidium and cesium.

18. A vapor-electric device comprising an enclosure-means, an anode, acathode, and a quantity of a discharge-metal within said device, saiddischarge-metal being selected from the group consisting of potassium,rubidium and cesium; said cathode including a metal tube-portionextending. interiorly into said enclosure-means, a portion of saidcathode-tube carrying metal fins at a region within the interior of theenclosuremeans, means for heating the inside of the cathode-tube at thefinned portion thereof, means for externally cooling the cathode-tube ina region where it enters the enclosure-means, said cathode-tube beinglong enough so that said cooled enclosure-entering region is the coolestpart of the device, whereby the discharge-metal condenses thereon, andmeans providing a cupshaped member surrounding said cooled region of thecathode-tube within the device, the open end of said cup-shaped memberfacing that end of the device, and an evacuating tube extending into thedevice to a point between that end of the device and the open end ofsaid cup-shaped mem ber.

JOHN L. BOYER. ROBERT J. BALLARD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,452,861 Mulder Nov. 2, 19482,456,896 Slack Dec. 21, 19%8

